Open your newly stitched “_stitched_injected.mp4” files in Quicktime and export under the “Apple Devices 4K” settings. This will compress the files slightly and reduce the quality, but allow them to work in your video editing system which is a huge plus over not opening at all.

You can also do this as a batch processor through an Automator script or through Apple Compressor by queing up all of your footage and letting it render while you get a cup of coffee or maybe a gin and tonic because you were frustrated at your go-to handheld 360 camera.